Digital wireless systems, such as wireless local area networks, or cellular devices, such as cellular telephones may exist in a number of different frequency bands and may each use a unique communication protocol. For example, cellular and GSM telephones may operate in the 750-960 MHz frequency band, PCS and UMTS may operate in a 1700-2170 MHz frequency band, and WIFI may operate in the 2.4-5.8 GHz bands.
However, cellular, PCS, UMTS, and WIFI are often used with different types of devices, each with a different functionality and data processing capability. Because of the different functionality, it is often necessary for service providers to provide simultaneous infrastructure access under each of the different protocols.
One complicating factor with providing simultaneous access is that access under the different protocols often occurs in a number of different environments. While the environment could also be out-of-doors, the environment could also involve use within a restaurant, theater or other user space. Such environments do not allow for the use of bulky antenna or antenna structure that detracts from the architecture of the space.
Another complicating factor is that cellular, PCS, UMTS, and WIFI often use frequency bands that are not harmonically related. As such, an antenna designed for one frequency band may not work with other bands.
One prior art solution to the problem of multiple frequency bands has been to combine a monopole antenna with a choke and a patch antenna to create a multi-band antenna structure. The patch may be conventional or include one or more slots for high frequency operation.
While, the use of the monopole and patch antenna is effective in some cases, the monopole antenna often experiences a phase reversal at high frequencies resulting in an elevation pattern split of a radiated signal. In addition where the patch antenna structure exceeds ¼ wavelength in high band frequencies, the radiated field has significant azimuth pattern distortion. Accordingly, a need exist for better antenna that operate in multiple non-harmonically related frequency bands.